Laundry detergent is a cleaning agent that is added to washing machines to remove dirt from clothing. Soap has largely been displaced by branched alkylbenzenesulfonates as the main cleaning agent in laundry detergents as soap is relatively ineffective in hard water. However, branched alkylbenzenesulfonates have been found to have poor biodegradable properties, and are often replaced with linear alkylbenzenesulfonates (LABs), as more biodegradable than the branched analogs. Surfactants are often classified according to the charge of the molecule or ion, the three main classes being anionic, neutral, and cationic detergents. Anionic detergents are most commonly encountered for domestic laundry detergents. The polar component allows the detergent to dissolve in the water, whereas the nonpolar portion solubilizes greasy (“hydrophobic”) materials that are the usual target of the cleaning process.
Detergent formulations, which describe an entire detergent product besides just the surfactants, generally contain several components. Three main ingredients of common detergent formulations are builders (50% by weight, approximately), the alkylbenzenesulfonate surfactant (15%), and bleaches (7%). Builders are water softeners, whose chemical compounds are agents that remove calcium ions by complexation or precipitation. Typical builders are sodium carbonate, complexation agents, soap, and zeolites. Builders function by sequestering or precipitating the problematic ions. One of the most common builders is sodium triphosphate, yet sodium triphosphate induces standing water eutrophication. Bleach refers to a number of chemicals which remove color, whiten, or disinfect, often by oxidation. Most bleaches in laundry detergents are oxidizers, e.g., sodium perborate or sodium hypochlorite. In addition, other agents are added as “bleach activators”, to enhance the effectiveness of the bleaching agent; a popular bleach activator is tetraacetylethylenediamine. Enzymes are macromolecular biological catalysts. Enzymes accelerate, or catalyze, chemical reactions. The amounts of enzyme typically may be up to about 2% by weight of a detergent product, and are required to degrade recalcitrant stains composed of proteins, fats, or carbohydrates, where each type of stain requires a different type of enzyme, i.e., protease for proteins, lipases for greases, and amylases for carbohydrates.
Detergent formulations include many other ingredients depending on the specific application. Such additives modify the foaming properties of the detergent product by either stabilizing or counteracting foam. Other ingredients increase or decrease the viscosity of the solution, or solubilize other ingredients. Corrosion inhibitors counteract damage to washing equipment. Dye transfer inhibitors act to prevent dyes from one article from coloring other items. Anti-redeposition agents are used to prevent fine soil particles from reattaching to the product being cleaned. In addition, a number of ingredients affect aesthetic properties of the item to be cleaned, or the detergent itself before or during use. These agents include optical brighteners, fabric softeners, and colorants. A variety of perfumes are also components of modern detergents, provided that the perfumes are compatible with the other components and do not affect the color of the cleaned item.
In spite of the range of detergent formulations that have been developed, it remains a problem that consumer washing machines using conventional detergents are ill-equipped to contend with heavy grease stained clothing. Typical conventional detergent formulations either fail to remove the grease in a single wash cycle or suffer from re-deposition of the grease onto the components of the washing machine such as the drum from which the grease can transfer to a next load of clothes placed in the washing machine.
While there are many types of detergents available, there still exists a need for a detergent formulation for heavy duty grease stains and automotive soils that leave clothing clean while preventing the re-deposition of removed soiling material from clothing or on the washing unit itself.